Rhodobacter sulJidophilus, a sulphide-tolerant, salt-tolerant member of the Rhodospirillaceae, was shown to produce molecular hydrogen on a mineral medium with lactate as electron donor and glutamate as nitrogen source. A maximum production of about 1.1 mmol H2 (mmol added lactate):' was found at pH 6-75. The in vivo activity of hydrogenase and nitrogenase showed that hydrogenase activity (and thus the H2 recycling system) was greatest at pH 6.5 and 6-75 and thus, at least partially, was responsible for the lack of Hz production below 6.75, but that nitrogenase activity was greatest at between pH 6.5 and 7.0, and decreased to zero at pH 8.0, resulting'in reduced H2 production at pH 7.5 and none at pH 8-0. When sufficient NH,+ had accumulated in the culture, nitrogenase activity remained below the maximum value and no H2 production occurred.

This study examines the isolation of poly(3-hydroxybutyrate) (PHB) from recombinant Escherichia coli XL1-blue pBHB2 OLD-2 harbouring the PHB biosynthesis gene. Six types of commercial surfactants (Emal 10P, Emal AD-25, Emal S PASTE, Neopelex S-S, Triton X-100 and cetyl trimethyl ammonium bromide (CTAB)) were screened for PHB isolation by solubilising non-polymer cellular material (NPCM) in the cell. Emal 10P, Emal AD-25, Emal S PASTE and Triton X-100 are suitable surfactants for PHB isolation. Factors such as the reaction temperature, reaction time, ratio of NPCM/surfactant and pH were investigated to achieve optimum conditions. For 80% of the PHB content in dry cells, the purity and recovery of the obtained PHB was 98% and 99% when 0.67 of NPCM/Emal S PASTE was used at 70 • C for 30 min. The cost of the used surfactant is below 0.5 USD/kg (PHB). The pretreatment and multistage digestion method must be combined when the PHB content is lower than 80%.

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